Stimulation of anatomical regions of a patient is a clinical technique for the treatment of disorders. Such stimulation can include deep brain stimulation (DBS), spinal cord stimulation (SCS), Occipital NS therapy, Trigemenal NS therapy, peripheral field stimulation therapy, sacral root stimulation therapy, or other such therapies. For example, DBS may include electrical stimulation of the thalamus or basal ganglia and may be used to treat disorders such as movement disorders such as essential tremor, Parkinson's disease (PD), and dystonia, and other physiological disorders. DBS may also be useful for traumatic brain injury and stroke. Pilot studies have also begun to examine the utility of DBS for treating depression, obesity, epilepsy, and obsessive-compulsive disorder, Tourette's Syndrome, schizophrenia, and other indications.
A stimulation procedure, such as DBS, typically involves first obtaining preoperative images, e.g., of the patient's brain, such as by using a computed tomography (CT) scanner device, a magnetic resonance imaging (MRI) device, or any other imaging modality. This sometimes involves first affixing to the patient's skull spherical or other fiducial markers that are visible on the images produced by the imaging modality. The fiducial markers help register the preoperative images to the actual physical position of the patient in the operating room during the later surgical procedure.
After the preoperative images are acquired by the imaging modality, they are then loaded onto an image-guided surgical (IGS) workstation, and, using the preoperative images displayed on the IGS workstation, a neurosurgeon can select a target region within the patient anatomy, e.g., within the brain, an entry point, e.g., on the patient's skull, and a desired trajectory between the entry point and the target region. The entry point and trajectory are typically carefully selected to avoid intersecting or otherwise damaging certain nearby critical structures or vasculature.
In the operating room, the physician marks the entry point on the patient's skull, drills a burr hole at that location, and affixes a trajectory guide device about the burr hole. The trajectory guide device includes a bore that can be aimed to obtain the desired trajectory to the target region. After aiming, the trajectory guide is locked to preserve the aimed trajectory toward the target region. After the aimed trajectory has been locked in using the trajectory guide, a microdrive introducer is used to insert the surgical instrument along the trajectory toward the target region, e.g., of the brain. The surgical instrument may include, among other things, a recording electrode leadwire, for recording intrinsic electrical signals, e.g., of the brain; a stimulation electrode leadwire, for providing electrical energy to the target region, e.g., of the brain; or associated auxiliary guidewires or guide catheters for steering a primary instrument toward the target region, e.g., of the brain.
The stimulation electrode leadwire, which typically includes multiple closely-spaced electrically independent stimulation electrode contacts, is then introduced and positioned in close proximity to the tissue targeted for sitmulation, to deliver the therapeutic stimulation to the target region, e.g., of the brain. An implanted pulse generator (IPG) generates electric pulses to transmit signals via the leadwire. The leadwire can include cylindrically symmetrical electrodes, which, when operational, produce approximately the same electric values in all positions at a same distance from the electrode in any plain that cuts through the electrode perpendicular to the central longitudinal axis of the leadwire. Alternatively, the leadwire can include directional electrodes that produce different electrical values depending on the direction from the electrode. The stimulation electrode leadwire is then immobilized, such as by using an instrument immobilization device located at the burr hole entry, e.g., in the patient's skull, in order for the DBS therapy to be subsequently performed.
The target anatomical region can include tissue that exhibit high electrical conductivity. For a given stimulation parameter setting, a respective subset of the neural elements are responsively activated. A stimulation parameter can include, for example, a current amplitude or voltage amplitude, which may be the same for all of the electrodes of the leadwire, or which may vary between different electrodes of the leadwire. The applied amplitude setting results in a corresponding current in the surrounding neural elements, and therefore a corresponding voltage distribution in the surrounding tissue.
After the immobilization of the stimulation electrode leadwire, the actual stimulation therapy is often not initiated until after a time period of about two-weeks to one month has elapsed. This is due primarily to the acute reaction of the brain tissue to the introduced electrode leadwire (e.g., the formation of adjacent scar tissue), and stabilization of the patient's disease symptoms. At that time, a particular one or more of the stimulation electrode contacts is selected for delivering the therapeutic stimulation, and other stimulation parameters are adjusted to achieve an acceptable level of therapeutic benefit. The IPGs offer a wide range of stimulation settings which can be independently or concurrently varied in order to correspondingly alter the size, shape, and location of the volume of tissue being therapeutically affected by the stimulation.
Systems and methods are provided that facilitate exploration of target regions of stimulation and stimulation therapies to determine which therapy regimen is best suited for a particular patient or group of patients.
A treating physician typically would like to tailor the stimulation parameters (such as which one or more of the stimulating electrode contacts to use, the stimulation pulse amplitude, e.g., current or voltage depending on the stimulator being used, the stimulation pulse width, and/or the stimulation frequency) for a particular patient to improve the effectiveness of the therapy. Parameter selections for the stimulation can be achieved, for example, via trial-and-error. However, the use of guiding visualization software provides for efficient stimulation parameter selection. See Frankemolle, A. et al., “Reversing cognitive-motor impairments in Parkinson's disease patients using a computational modelling approach to deep brain stimulation programming,” Brain 133 (3): 746-761 (2010). Indeed, systems and methods are provided that provide visual aids of the electrode location in the tissue medium along with computational models of the volume of tissue influenced by the stimulation, thereby facilitating parameter selection. See, for example, U.S. patent application Ser. No. 12/454,330, filed May 15, 2009 (“the '330 application”), U.S. patent application Ser. No. 12/454,312, filed May 15, 2009 (“the '312 application”), U.S. patent application Ser. No. 12/454,340, filed May 15, 2009 (“the '340 application”), U.S. patent application Ser. No. 12/454,343, filed May 15, 2009 (“the '343 application”), and U.S. patent application Ser. No. 12/454,314, filed May 15, 2009 (“the '314 application”), the content of each of which is hereby incorporated herein by reference in its entirety. Those applications describe systems including equation-based models for generation of VOAs based on input of stimulation parameters. The described systems and methods provide for estimation of stimulation volumes and display models of a patient anatomy and/or a stimulation leadwire, via which to graphically identify the estimated stimulation volumes and how they interact with various regions of the patient anatomy. If a physician selects a putative therapeutic stimulation parameter combination, the software displays a representation of the volume of surrounding tissue which is estimated to be activated by the system. See also S. Miocinovic et al., “Cicerone: stereotactic neurophysiological recording and deep brain stimulation electrode placement software system,” Acta Neurochir. Suppl. 97(2): 561-567 (2007).
U.S. Prov. Pat. App. Ser. Nos. 61/521,583 (“the '583 application”), filed Aug. 9, 2011 and 61/690,270 (“the '270 application”), filed Jun. 22, 2012, each of which is hereby incorporated by reference in its entirety, further describe generation of a VOA on a fiber specific basis.